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WORLD INTELLECTUAL PROPERTY ORGANIZATION
Intemational Boreao

INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCI)

(51) iDfeinadonal Pateot Qassilicafion ^ :
• 020^54,1/26,1/28

(11) Intttnational PoblicatioD Nnmber: WO 92/22669

(43) Intenodoiial Pnblication Date: 23 December 1992 (23.12.92)

(21) International Application Nnmber:

(22) International FlIiDg Date:

(30) Priority data:
9113212.6

PCT/GB92/01116
19 June 1992(19.06.92)

19 June 1991 (19.06.91)

(71) Applicant (for all designated States except US): HYPO-

GUARD (UK) LIMITED IGB/GB]; Dock Lane. Mel-
ton, Woodbridgc, Suffolk IP12 IPE (GB).

(72) Inventor; and

(75) inrentor/Applicant (for US only) : GULLICK. Stephen. Pe-
ter [GB/GB]; 18 Deben Avenue. Martlesham. Ipswich,
Suffolk IPS 7PQ(GB).

(74) Agent: DUMMETT. Thomas, Ian, Peter; Dummett Copp
& Co., 14 The Square, Martlesham Heath, Ipswidh, Suf-
folk IPS 7SL (GB).

(81) Designated States : AT. AT (European patent), AU. BB, BE
(European patent), BF (OAPI patent). BG, BJ (OAPI
patent), BR, OA, CF (OAPI patent), CG (OAPI patent),
CH, CH (European patent), CI (OAPI patent), CM
(OAPI patent), CS, DE. DE (European patent), DK,
DK (European patent), ES, ES (European patent), FI,
FR (European patent), GA (OAPI patent), GB, GB (Eu
ropean patent), GN (OAPI patent). GR (European pa^
tent). HU, IT (European patent), JP, KP, KR, LK, LU.
LU (European patent), MC (European patent), MG. ML
(OAPI patent), MN, MR (OAPI patent), MW. NL> NL
(European patent), NO. PL. RO, RU, SD. SE, SE (Euro-
pean patent), SN (OAPI patent), TD (OAPI patent), TG
(OAPI patent), US.

Published

WIdi international seardt report
Brfore the expiration of the time limit for amending the
claims and to be nepublished in the event of the receqft of
amendments*

(SQTMe: REAGENT MIXTURES FOR GLU<X)SE ASSAY

(57) Abstract

The present mvention relates to a test reagent mixture composition comprising the enzymes glucose oxidase and peroxi-
dase and a chromogen which interacts with the hydrogen peroxide from the oxidation of the blood glucose by the glucose oxi-
dase, characterised in that the glucose oxidase and the peroxidase are present in proportions which provide from 300 to 700 Inter-
national Units (lUs) of glucose oxidase and at least 20 Intemational Units of peroxidase and m that the chromogen is present in
an amount which provides from 12 to 20 grams of active chromogen per 500,000 Intemational Units of ghicose oxidase. Prefer-
ably, the composition is put up in a low molecular weight gelatin matrix and is impregnated into a mioto-porous earner mem-
brane.

FOR TUB PURPOSES OF INFORMATION ONLY

Codes used to identily Slates |)any to the PCI* on Che from pag^* of {lamphlets publishing internalional
applications under the PCT.

Austria

MakinJ

MI.

Mali

Australia

France

Mooeolia

BartaUos

Gabon

MawrftitrHi

Uoittxl KtitsJuin

Malawi

Bttritifia l*aso

Guinea

Nmbcrlamb

Otceos

Norway

Hungary

PolamI

Brax9

IrdaMi

Romania

CVijuIa

Italy

Russian Federation

O^atml ATricaa Republic

Japan

Sudan

Cbngu

Uemocralic Pcopli:'^ Republic

Sweden

5wil»:rland

of Korea

C8ledlvi4nr

Republic or Korea

Soviet tJnIon

Liucbtcmtda

Chad

f jmNxtiuvaLia

Sn Lania

Togo

Gcimaoy

I4i

Luu;nibour|(

United Slates of America

Denmark

Monaco

Spain

wo 52/22669

PCr/GB92/01116

REAGENT MIXTURES FOR GLUCOSE ASSAY

The present invention relates to a reagent mixture, notably to
a mixture of analytical reagents in a carrier gel which
5 provides enhanced consistency of the colour generated with the
elapse of time.

. BACKGROUND TO THE TNVTgTTPTm-

Blood samples are often assessed for the amount of glucose or
some other constituent therein by reacting. the blood with one
or more reagents carried on a test . stick or pad so as to
develop a colour which can be observed by an operator." For
example, a reagent pad can contain the enzymes glucose oxidase
15 and peroxidase and o-tolidine as the chromogen which turns blue
as the glucose oxidase oxidises glucose in the blood sample to
gluconic acid and hydrogen , peroxide. The hydrogen peroxide
reacts in the presence of the peroxidase with the o-^tolidine to
give a blue colour whose intensity depends upon the amount of
20 hydrogen peroxide released and hence the amount of glucose in
the blood. The reagents are usually put up in a gel matrix,
for example of a natural gel, for example a gelatin, or of a
synthetic polymer, for example a polyvinylpyrrolidone.

However, problems arise in that the colour is affected by the
time over which the blood sample is held in contact with the
reagent pad, as well as the amount of blood in contact with the
reagents. it is therefore customary for such tests to be
carried out within a strictly monitored time schedule and the
30 results are often of dubious value due to inaccuracies in
observing the time schedule.

Surprisingly, we have found that the proportion of the reagents
to one another in the matrix affects the period over which a
consistent colour is produced by the interaction of the blood
with the reagent. If the proportions in the mixture lie within

wo 92/22669

2 -

PCT/GB92/01116

certain limits, the colour produced is sufficiently constant
over a period of time for the need for strict adherence to a
time schedule to be reduced.

5 snMMftRY OP THE INVENTION;

Accordingly, the present invention provides a blood test
reagent mixture composition comprising the enzymes glucose
oxidase and peroxidase and a chromogen which interacts with the

10 hydrogen peroxide from' the oxidation of the blood glucose by
the glucose oxidase, characterised in that the glucose oxidase
and the peroxidase are present in proportions which provide
from 300 to 700 international Units (IDs) of glucose oxidase
and at least 20 International Units of peroxidase and in that

15 the chromogen is present in an amount- which provides from 12 to
20 grams of active chromogen per 500,000 International Units of
glucose oxidase. Preferably, the glucose oxidase is present in
from 400 to 550 lUs per 27.5 to 32.5 lUs of peroxidase and the
chromogen is o-tolidine which is present in an amount of from

20 12 to 15 gs per 500,000 lUs of the glucose oxidase i

It is preferred that the reagent mixture be put up in a gel
matrix, notably a gelatin matrix, which provides from 200 to
400 gs of the matrix on a dry weight basis per 500,000 lUs of
25 the glucose oxidase.

It is particularly preferred that the reagent mixture/matrix be
absorbed in a micro-porous membrane carrier.

30 oaie enzymatic reagents as used herein can be present in any
suitable form, for example as the dry powdered active enzyme or
as a precursor or addition product thereof which under the
conditions of the test to be carried out produces an active
enzyme in the reagent mixture. Thus, the enzymatic reagent can

35 be an active enzyme, for example glucose oxidase or peroxidase,
or a stabilised form thereof, for example an acetate or other

wo 92/22669

- 3 -

PCT/GB92/011I6

salt or adduct thereof, which releases the active enzyme when
the reagent mixture is wetted.

For convenience, the invention will be described hereinafter in
5 terms of a mixture of glucose oxidase and peroxidase as
conventionally used in the assessment of glucose in a blood
sample.

Similarly, the term chromogenic material is used herein to
denote any material which develops a property upon interaction
with one or more of the products produced when the enzymatic
reagent reacts with the blood sample to be assessed. Thus, the
term includes materials which develop ultraviolet fluorescence
or other detectable but not visible properties. However, it is
preferred that the chromogenic material be one which develop a
colour within the visible spectrum, for example as when di-
anisidine or o-tolidine reacts with the hydrogen peroxide
released when glucose in blood interacts with the glucose
oxidase in the reagent mixture. The chromogenic material can
be used in the form of the active material or a precursor or
adduct thereof, notably an inorganic acid salt thereof such as
the hydrochloride or sulphate, which releases the active
ingredient during the test.

25 For convenience, the invention will be described hereinafter in
terms of o-tolidine as the chromogenic material.

The enzymatic reagent and chromogenic material are operatively
associated with one another so that they can interact under the
condiUons of the test procedure. Typically, the reagent and
the chromogenic material will be put up in physical admixture
with one another. However, it is within the scope of the
present invention to put up the reagent and chromogenic
material in a two part form which is admixed immediately prior
35 to use; or in a form in which the reaction products of the
interaction of the enzyme reagent with the glucose in the blood

wo 92/22669

- 4 -

PCr/GB92/01116

saii5)le diffuse into a zone containing the chromogenic material
to develop the colour therewith separately from the enzyme
interaction zone. Thus, for example, the enzyme reagent can be
concentrated at one end or one side of a reagent pad and the
5 chromogenic material at the other end or side.

For convenience, the invention will be described hereinafter in
terms of a pad of the reagent mixture containing the enzymatic
reagent and the chromogenic material substantially uniformly
10 distributed throughout the pad.

The reagent mixture may contain other materials as is
customary, for example phosphate buffering agents,
preservatives, anti-coagulants or surface active agents. Such
15 other materials are typically inert to the material to be
tested, the other constituents of the reagent mixture and the
products- of the reactions and interactions which occur during
the test procedure. Such other constituents can be present in
the amounts normally used in such reagent mixtures.

AS stated above, we have found that if the enzjinatic reagent
and chrcanogenic material are present in the reagent mixture
composition within specified proportions, the colour which the
interactions- between the material being assessed and the

25 various con^jonents of the mixture is surprisingly stable and
enables the colour to be observed over a wider period of tiine
than hitherto. Thus, the enzymatic reagents will typically be
present in proportions of from 400 to 600, notably 450 to 550,
International Units (lUs) of glucose oxidase and at least 20

30 lUs^ l^ically about 27.5 to 35 lUs of peroxidase in the
mixture. The chromogeiiic material will typically be present in
an amount of from 12 to 17, notably from 13 to 16, grams per
500,000 lUs of the glucose oxidase. The optimum proportions
within these ranges can be determined for any given case and a

35 given carrier by sinple trial and error tests.

wo 92/22669 PCr/GB92/01116

~ — 5 *•

As stated above, the reagent mixture is preferably put up in a
matrix carrier medium so that the material to be assessed can
penetrate to the enzyme reagent and the chromogenic material .
The matrix can be provided by a natural gum, jelly or gel, for
example a gelatin, agar agar, aspic or silica gel; or can be
provided by a synthetic polymer gel, for example a cellulosic
gel or a polyvinylic resin gel. For convenience, the invention
will be described hereinafter in terms of the use of a gelatin
gel as the carrier matrix.

The gel matrix can carry the enzymatic reagent and chromogenic
material substantially uniformly distributed throughout it.
This is conveniently achieved by mixing the enzyme reagents
into a premix of the gelling agent and the. chromogenic

15 material; and allowing the mixture to set in the desired form.
Alternatively, the enzyme reagent and the chromogenic material
can be admixed with a thixotropic gel carrier which is worked,
for example by being stirred, to maintain it in the fluid state
during mixing, but which is then allowed to set for storage and

20 transport prior to use.

Alternatively, the matrix may contain the enzymatic reagent and
chromogenic material non-uniformiy distributed therein, as when
a gel layer is formed which has a high concentration of the gel

25 matrix in its upper layers to act a protective layer or Coating
for the reagent rich lower layers; or where the enzymatic
reagent is located in a separate zone of the matrix from that
containing the chromogenic material, in this case, the product
from the interaction of the material being tested with one or

30 more of the enzymatic reagents diffuses from the enzyme zone
into the zone containing the chromogenic material to develop a
colour as a separate stage in that zone.

For convenience, the invention will be described hereinafter in
35 terms of a reagent mixture which is uniformly distributed
throughout a gelatin matrix.

•If.

wo 92/22669

- 6 -

PCr/GB92/01116

Bie matrix carrying the reagent mixture can be put up in a
number of physical forms, for exan^le as test strips or discs
in which a pad of the matrix is applied to one face of the
strip or disc and the colour resulting from the interaction of
5 the material under assessment and the reagents and materials in
the matrix is observed visually against the white background of
the support strip or disc or against a separate reference
background. Alternatively, the matrix can be put up in a
series of zones through which Uie reagent mixture is

10 distributed so that the interaction of the material to be
assessed with the enzyme occurs in one zone and the product of
that interaction diffuses to a second zone in vrtiich the colour
reaction takes place. In a further alternative, the reagent
mixture matrix can be absorbed or impregnated into the pores of .

15 a porous carrier to one face of which the material to be
assessed is applied and the colour developing within the matrix
is viewed from the opposite surface of the carrier.

For convCTience, the invention will be described in terms of
20 the use of a pad or disc of a micro-porous membrane which is
inqpregnated with the reagent matrix.

In a conventional blood test reagent mixture, the gel matrix is
a high molecular weight gelatin irtiich is present in about 4% by

25 dry weight. However, where the reagent mixture is to be
absorbed into a micro-porous membrane, we prefer to use a low
molecular weight gelatin, typically with a molecular weight in
the range 20,000 to 50,000. Where such a gelatin is present in
the amounts used hitherto, we have found that this results in

30 a gel matrix \diich cannot be held satisfactorily within the
pores of the manbrane. On this other hand, we have found that
if the gel content of the reagent mixture conposition racceeds
about 20% by dry weight, the gel inhibits the diffusion of
reaction products through the membrane and hence development of

35 a colour reflecting the true extent of the interactions which
have occurred. We therefore prefer to provide the gel inatrix

wo 92/22669

- 7 -

PCr/GB92/01]16

as a low molecular weight gelatin in an amount of from 250 to
325 gs by dry weight per 500,000 lUs of the glucose oxidase
present in the reagent mixtrue.

The invention will now be illustrated by the following Example
in which all parts and percentages are given by weight unless
stated otherwise.

A first solution was made by stirring together at . room
temperature 300 mis of de-ionised water, 200 mis of 0^5 Molar
sodium phosphate buff er to give a pH of 7> 100 mis of a 20% w/v
solution of the surfactant Gantrez and 300 gs of dry powdered
gelatin having a molecular weight in the range 25,000 to
40,000.

A second solution was prepared by stirring together at 60«» c
for one hour 300 mis of de-ionised water, 300 mis of
methoxyethanol and 15 gs of o-tolidine hydrochloride or
dianisidine hydrochloride.

The second solution was mixed dropwise with stirring into the
first solution and the mixture stood for i hour at 60" c.

A third solution was mad^ up by mixing 500,000 lUs of glucose
25 oxidase and 30,000 lUs of peroxidase in a 0.1 Molar solution of
the spdium phosphate buffer. This solution was mixed with
stirring into the other mixed solutions and filtered through a
0.1 micrometre aperture filter. . .

30 The resultant solution was impregnated into a polysulf one resin
sheet (0.2 to 0.4 mms thick and having an average pore diameter
of 0.2 micrometres and an air permeability of 3 litres per
minute per square centimetre at an applied pressure of lo psig)
to provide 5 lUs of glucose oxidase, 3 lUs of peroxidase, 0.2

35 milligrams of o-tolidine and 4 milligrams of gelatin per square
centimetre of the membrane.

wo 92/22669

- 8 -

PCr/GB92/pill6

By way of coiaparison, the same membrane was iinpregnated with a
conventional reagent mixture to provide the conventional level
of enzyme and chromogen per square centimetre.

Blood saH5>les were applied to the faces of a number of 6 mms
diameter discs cut from each of the membranes. With the
reagent compositions of the invention, a blue colour developed
after only 10 seconds. The hue and intensity of the colour
became stable after about 30 to 40 seconds and remained stable
for a further 30 to 40 seconds, thus allowing considerable
lattitude for the time to observe the colour. By way of
Goi.5)arison, the conventional formulations gave a colour which
deepened in hue and intensity over 10 to 30 seconds after
applying the blood sample, but which degenerated after a
further 15 seconds, giving little or no lattitude in the time
for observing the true colour.

From another aspect, the present invention provides a method
for making a test reagent mixture of the invention, wherein the
20 components of the mixture are admixed with one another to
provide a substantially uniform mixture of the components.

The invention further provides a method for making a test
reagent mixture carried on a micro-porous carrier medium,

25 wherein a fluid reagent mixture of the invention is applied to
the carrier medium. Prefferably, the mixture is applied by
impregnating the medium, f or exan^le by padding a sheet of the
carrier through a bath of the reagent mixture, and allowing the
mixture to gel within the pores of the carrier. Preferably,

30 the gelled mixture blinds the bores of the pores of the carrier
so that rupture of blood or other cells due to capillary acUon
by the pores is reduced. Discs or other shapes can be cut from
the impregnated carrier for mounting on tests sticks having
apertures therein or as the end walls of sample receivers so

35 that the colour which develops in the carrier can be observed
from the opposite side to that to which the blood is applied.

wo 92/22669

- 9 -

PCr/GB92/01116

CLAIMS!

1. A blood test reagent mixture composition comprising the
enzymes glucose oxidase and peroxidase and a chromogen which

5 interacts with the hydrogen peroxide from the oxidation of the
blood glucose by the glucose oxidase, characterised in that the
glucose oxidase and the peroxidase are present in proportions
which provide from 300 to 700 International Units (lUs) of
glucose oxidase and at least 20 International Units of
io . peroxidase and in that the chromogen is present in an amount
which provides from 12 to 20 grams of active chromogen per
500,000 International Units of glucose oxidase,

2. A test reagent mixture as claimed in claim 1,
15 characterised in that the glucose oxidase is present in from

400 to 550 lUs per 27.5 to 32.5 lUs of peroxidase and the
chromogen is o-tolidine which is present in an amount of from
12 to 17 gs per 500,000 lUs of the glucose oxidase.

20 3.. A test reagent mixture as claimed in either of claims 1 or.
2, characterised in that it is put up in a gel matrix.

4. A test reagent mixture as claimed in claim 3,
characterised in that the* gel matrix is a gelatin matrix, which

25 provides from 200 to 400 gs of gelatin on a dry weight basis
per 500,000 lUs of the glucose oxidase.

5. A test reagent mixture as claimed in any one of the
preceding claims, characterised in that the reagent mixture is

30 carried by a micro-porous membrane.

6 . A test reagent mixture as claimed in either of claims 4 or
5, characterised in that the gelatin has a molecular weight in
the range 20,000 to 50,000 and is present in an amount of from

35 250 to 325 gs by dry weight per 500,000 lUs of the glucose
oxidase.

wo 92/22669

- 10 -

PCr/GB92/01I16

7 . A test reagent mixtiire according to claim 1, substantially
as hereinbefore described in the Exanple.

8 . A method for making a test reagent mixture as claimed in
5 claim 1, characterised in that the components of the mixture
are admixed with one another to provide a substantially uniform
mixture of the con^onents .

Si A method for making a test reagent mixture as claimed in
10 claim 5/' ch^cterised in that a fliiid reagent mixture as
claiiied in any oiie of claims 1 to 4 or claim 6 is intpregnated
into the pores of a micro-porous carrier membrane.

id. A method for testing blood samples, characterised in that
15 it comprises applying blood to a test reagent Mxture as
clcdined £h claim 1 and observing the colour which develops.

11, A method as claimed in claim 10, characterised in that the
reagent raixtxire is carried by a micro-porous carrier membrane
20 and the blood is applied to one face of the membrane and the
colour is observed from the opposite face of the m«nbranei

INTERNATIONAL SEARCH REPORT

IntemationaJ Application No

PCT/GB 92/01116

I. CLASSIFICATION OF SUBJECT MATTER (if severaJ dassfficxtioD symbols apply, indicate aU)^

Accordiog to IntematiDnai Patent ClassifiottoD (IPC) or to both National GassUicatioo and IPC

Int. CI. 5 C12Q1/54;

C12Q1/26;

C12Q1/28

II. FIELDS SEARCHED

MintUDni DocBBCUaiion Scardied'

Cbssificatioa ^ystan

Cl ass ifi cation Symbols

Int.Cl. 5

C12Q

Doaimcatation Searched other than Miftlmum DocomcntatfoD
to the Extent that ach Docaments are Induded lo the Fields Searched'

m. DOCUMENTS CONSIDERED TO BE RELEVANT*

Otcgmy*

ChadoD of Docmncst, U iritbiBdIcatiOB, where appioprfate, of the idevaai passages l^

Rdmat to Claim Nb.*1

US,A,4 340 669 (R. BAUER)

20 July 1982

see the whole document

l-ll

EP,A,0 016 94> (BOEHRINGER MANNHEIM GMBH.)

15 October 1980

see the whole' docunent

l-ll

FR,A,2 295 425 (B10EHRIN6ER MANNHEIM GMBH.)

16 July 1976

see -the wbole .docunent

1-11

'GB,A,893 3181nILES LABORATORIES, INC.)

4 April 1962 .

see the whole 'document

1-11

" Spedal calqpiln cf cM dodBDenis t

*A' dooanent defining the geaeial state of the art vifaicfai5 not
consfderedtobeof partuttbrrctevaojDe ■

earlier doanncot hot published on or after the Intcmatioaal
fiiiog date '

*L' docomest wfaicb may throw donbts on prloiity dshnCs) or
which is dted to establish the puliUcattoQ da^ of anctfttr
dtation or other spcdal reason (as spccsScd)

"O' docamem rcfenibgtoaa ofaldisdosore, nsc^ csdiibttioD or-
other means

docomest pabOs hed pr ter to tte hitcmatio&al 6Bag date but
later than the piioiity date datncd

later docnmcnt published after the intemattonal filing date
or priority date and not in cooma with the appficatioa hot
dted to Bodcmaad the principle or theory iDuleiiyiiig tbt

'XT docuneot of paxticoiar relcvaiices the clilnied fawcntloD
cannot be cntsidcred novel or csunst be ccpslderri to
involve ao inventive step

t of particniar reSevancc; the dalwed uveutioB
I be coosidcfcd to involve an nventtare step when the
test is combined with one or more other socb docsK
i» SBch combination being ohvfoos to a person sftlUed
intbeait.

'ft* docBnent ntenib e r tf the same patent faniQy

IV. CERIIFICATION

Date of the Actual Csmpleifan of the btteniadeoal Search

02 OCTOBER 1992

Date of Maffiag of tUs Intenatfosal Search Report

lutcniaiional Searching Anthority

EUROPEAN PATEOT OFnCE

Signatnre of Asthorixed Officer >^

Fflm FCryiSAmo tMcaed Mawy m

ANNEX TO TOE INIEM^^ONA^^^^^^ 9201116
ON INTERNATIONAL PATENT APPLICATION NO. g^gg^

PoUiartion

US-A-4340669

20-07-82

EP-A-0016947

15-10-80

FR-A-2295425

16-07-76

PauotfunBr

GB-A-893318

AT-T-

AU-B-

CA-A-

EP-A,B

JP-C-

JP-A-

JP-B-

US-A-

9821
524238
1157749
0058334
1311966
57146599
60035118
4391905
4391906

DE-B-
AT-T-
AU-B-
AU-A-
CA-A-
JP-C-
JP-A-
JP-B-
US-A-

2913553
4126
515851
5677980
1152871
1111586
55135599
56046800
4517287

DE-A-
AT-B-
AU-B-
AU-A-
BE-A-
CA-A-
CH-A-
DE-C-
GB-A-
GB-A-
JP-A-
JP-C-
JP-A-
JP-B-
ML-A-
SE-B-
SE-A-
US-A^.

2460903
350189
504794
8755775
836789
1060906
619048
2462952
1464360
1464359
54036237
1263517
51089491
54003394
7514628
458687
7514196
4385114

US-A- 3012976

PuUicsCioii -
date

15-10-84

09- 09-82
29-11-83
25-08-82
11-04-86

10- 09-82
13-08-85
05-07-83
05-07-83

09-10-80
15-07-83
07-05-81
09-10-80

30- 08-83

31- 08-^82
22-10-80
05-11-81
14-65«^d5

24H)6-^76
10-05-79
01-11-79
23r06-77
18-05-76

21- 08-79
29-08-80
01-10-87
09-02-77
09-02-77
16-03-79
16-05-85
05-08-76
22^2-79

23- 06^76

24- 04-89

22- 06-76
24-05^B3

St (tor mete deiaat abeat tfab a

; OScU Jminl «f the EnroptMi FMtiit Office, No. 12/82

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